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' TTORNEK Patented May 8, 1888.

..Illlllllll E: llllv (No Model.) E. NEW. PRATT. Y APPOETIIONING EUENA'GE DRAFT EOE BATTERIES '0El STEAM EoILEEsL.l No. 332,489.4

' WITQ/ VAESSES l tioning of the total to each furnace being regu` lated by the temperature of the escaping gases UNITED :STATES NAT. W. PRATT, OF BROOKLYN NEW YORK.

PATENT OFFICE.

APPORTIONlNG FURNACE-DRAFT FOR BATTERIES OF STEAM-BOILERS.

SPECIFICATION forming part of Letters Patent No. 382,489, dated May'8, 1888 Application-tiled-Junc 23, 1887. Serial No. 242.209. (No modeLl To @ZZ whom, it may concern.-

Beit known that I, NAT. W; PRATT, a citizen of the United States, residing at Brooklyn, county of Kings, and State of New York, have invented certain new and useful Improvements in Apportioning-FurnaceDrafts for Batteries of Steam-Boilers, of which the following is a specification. A

This invention relates to apparatus for automatically controlling the amount of air supplied to steam-boilerfurnaces according to the rate of combustion required in order to maintain a given pressure of steam; and the object of the invention is to so apportion the total amount of air supplied to the furnaces of the whole battery of boilers that the several-fires shall be soonest'equalized by delivering to each the different amounts of air which their different conditions may require, such equalizaf,

tion being intended for the purpose of increasing the efficiency of the steam regulation under violent fluctuations in the amount of power consumed. A

In order to effect thisfequalization the invention consists in employing a double system of draft-regulation, the total air-supply being regulated by the steam-pressure, the apporofthe same, respectively.

`In the accompanying drawings a battery ofA three boilers is represented in diagram, the

form chosen, for clearness of illustration, be- .ing of the locomotive type, although the invention is obviously applicable to all forms.

Figure 1 is a plan view.; Fig. 2, a sectional elevation of the systcmtaken on the line xx,- and Fig. 3, asimilar view taken onthelineyy. Ais the common flue through which the draft is conveyed from the several boilers, B C D, composing the battery. E is the air-pipe employed for conducting the air beneath the grates at a, Fig. 2.

The features of the invention are applicable to either a forced blast or a natural draft, and the draft-controlling apparatus shown is applicable to both methods.

F is the common drum or steam conductor, connecting and leading from the several boil= ers to the point of steam-eduction.

b is the main damper which governs the total amount of air supplied to the whole battery of boilers, the said damper being controlled by the action of the varying steam-pressure upon the flexible diaphragm of the pressureregulator c, increasing or decreasing they total' air-supply as more or less steanris consumed.

rlhe auxiliary dampers d, Vprovided inthe draft-pipe at'its severalb'ranches or points of entrance to the furnaces, or the auxiliary dampers e, placed at the points of exit of the furnace-draft to the flue A, orl both/sets of dampers, are connected to and regulated by the thermostat pressure-regulators f, the latter being` actuated bythe expansionL or conf traction of fluid within the bulbs g exposed to the temperature of the escaping gasesifrom each furnaceindependcntly;

The pipe E may be employed for conducting either a forcedor a natural draft. The

dampers d and dampers c serveident-i'cal functions, whether the draft be forced or natural, and said double sets of damp'ers d and c may vbe used singly or together, the different argenerated automatically holds the pressure,

approximately to the desired point under varying demands for steam; but the efficiency ofy a general 'draft-control system in which the regulation is extended only to the totalA airsupply as applied to a battery of lboilers is 1imited,`especially in cases where thefamount of power required fluctuates very violently, inasmuch as the dierent conditionsofthe various fires may require specific amounts of airsupply to control them with quick response. :For illustration, given abattery of three boilers having their fires at differentcondi-k tions or periods of activity, the fire which has reached the best condition will, receiving the full supply of air, be rapidly forced and comparatively soon burned out while contributing the greatest amount of heat. The furnace which has been freshly charged with fuel Will be developing the least share of heat, and,

while supplied with-the same amount of air as the one previously described, will take some time to reach an equal condition, Whereas the third furnace, having its fire nearly burned out, would not receive a greater proportion of air than its condition required. To compensate for these varying conditions, the auxiliary dampers d and dampers e, or both in coni5 junction, are operated by the fluctuations in temperatures of the fires by means of the thcrmostats g and iiexible diaphragms of the regulators f, so as to close said dampers if the temperature of the escaping gases is higher than thenormal and open them when theirtem perature is low, thus decreasing the specific air-supply to the furnace delivering the highest temperature,and vice versa. The lires becoming equalized, the effectiveness of the total air-regulation as controlled by the damper b is materially extended,aud therefore increased in its rapidity of action by reason of the uniformity of combustion promoted throughout the several fires.

The method of practicing my invention forms the subject-matter, and is claimed, in a separate application filed by me January 10, 1888, Serial No. 260,315.

Having thus fully described my invention,

what I claim, and desire to secure by Letters 35 In an apparatus for controlling the air-supply tothe furnaces of a battery of steam-boilers, the combination of a main draft-regulator, automatically governed by the iiuctuation of steam-pressure within said boilers and arranged to control the total airsupply with 

